The present invention relates to the preparation of new aromatic polyester compounds represented by the following general formula (I); this deals specifically with following sequence of recurring units: ##STR1## wherein, X and Y represent substituents selected from the group consisting of H, Cl, Br, a phenyl group and a C.sub.1 -C.sub.4 alkyl group;
n is a positive integer from 1 to 4, indicating the number of X and Y substituents; PA1 k,l,m,x, . . . z are positive integers from 1 to 1500; and EQU [k/(k+l+m+x+ . . . +z)].times.100=a, PA1 n is a positive integer from 1 to 4, indicating the number of X and Y substituents; and PA1 k is a positive integer from 1 to 1500. PA1 n is a positive integer from 1 to 4, indicating the number of X and Y substituents; PA1 k,l,m,x, . . . z are positive integers from 1 to 1500; and EQU [k/+l+m+x+z].times.100=a PA1 n is a positive integer from 1 to 4, indicating the number of X and Y substituents; and PA1 k is a positive integer form 1 to 1500. PA1 n is a positive integer from 1 to 4, indicating the number of X substituents; PA1 n is a positive integer from 1 to 4, indicating the number of Y substituents; hydroquinone diacetate (H--HD), chlorohydroquinone diacetate (Cl--HD) bromohydroquinone diacetate(Br--HD), methylhydroquinone diacetate (CH.sub.3 --HD) and phenylhydroquinone diacetate, etc. PA1 n is a positive integer from 1 to 4, indicating the number of X and Y substituents; PA1 Grade A: below five times PA1 Grade B: 6-11 times PA1 Grade C: 12-16 times PA1 Grade D: more than 17 times PA1 Grade E: impossible to eject below the decomposition temperature
where a=20 to 100%. In this case, if "a" is 100%, the said polyester turns into the polymer which is represented by the following general formula (II), which has the following sequence of recurring units. ##STR2## wherein, X and Y represent substituents selected from the group consisting of H, Cl, Br, a phenyl group and a C.sub.1 -C.sub.4 alkyl group;
Prior polyester compounds represented by polyethylene terephthalate have been widely used in fiber, film, plastics, etc, but there was much room for improvement of their tenacity and heat resistant properties.
Aromatic polyester compounds developed to meet such demand, were liquid crystal, which had a high modulus, high tenacity and low extensity. However, due to the high melting point and melt viscosity, processing was a very difficult problem. Recently, in order to overcome these problems a process for preparing copolymers, consisting of three or four differnt monomers, has been studied.
However, said co-polymer easily took the form of a block co-polymer, or somtimes a random co-polymer because of the inevitable discrepancy of reactivity among the monomers. As a result in addition to the physical properties of the resulting polymer, the melting point and melt viscosity, varied greatly with the reaction conditions, therefore quality control was very difficult.
In particular, a manufacturing process for an aromatic polyester consisting of a 4-hydroxybenzoic acid derivative, a diol of the hydroquinone series and isophthalic acid, said acidolysis method (U.S. Pat. No. 3,637,595), and phenolysis method (Japanese patent laid open No. 56-90,829) have now been disclosed. But in the operation of acidolysis method, if hydroquinone diacetate, 4-acetoxybenzoic acid and isophthalic acid are polymerized in accordance with a prior method, a partial block, consisting primarily of 4-acetoxybenzoic acid is formed in the polymer. This is the reason why the reactivities of said three ingredients are different from each other.
Consequently, the resulting polymer has no practical use because it has not only a high melting point and melt viscosity, but also an inferior processing ability, especially for spinning.
The phenolysis method proposed to solve the above problems. In this method hydroquinone, 4-hydroxybenzoic acid phenyl ester and diphenyl isophthalate are polymerized. But this method did not solve the problem which was caused by the discrepancy of reactivity among the monomers. The color of the polymer became black and the molecular weight dropped, because the --OH radical of hydroquinone oxidizes to a quinoid very easily.
In order to solve the problems of prior methods, the following method was invented. A new monomer, 4-acetoxy-(4-acetoxy phenyl)benzoate derived from hydroquinone diacetate and 4-acetoxybenzoic acid, is used as a unit of polymerization.